Metal injection molding multiple dissimilar materials to form composite electric machine rotor and rotor sense parts

ABSTRACT

A method for forming composite motor parts of two or more dissimilar materials by injection molding. Two or more different powder materials are injected under heat and pressure into cavities of a cylindrical-shaped mold and allowed to solidify to form a composite green compact. The final part may be used in machines of the type including permanent magnet, synchronous reluctance, switch reluctance and induction machines.

FIELD OF THE INVENTION

[0001] This invention relates generally to composite electric machinerotors and rotor sense parts, and more particularly, to the manufactureof rotors and rotor sense parts by injection molding.

BACKGROUND OF THE INVENTION

[0002] It is to be understood that the present invention relates togenerators as well as to motors, however, to simplify the descriptionthat follows, a motor will be described with the understanding that theinvention also relates to generators. Plastic injection moldingtechnology is well known to the plastics industry for producing parts ofsimple and complex geometry. The plastic injection molding processinvolves heating a plastic feedstock until it reaches a state offluidity, transferring the fluid plastic under pressure into a closedhollow space referred to as a mold cavity, and then cooling the plasticin the mold until it again reaches a solid state, conforming in shape tothe mold cavity.

[0003] The metal injection molding (MIM) process combines the structuralbenefits of metallic materials with the shape complexity of plasticinjection molding technology. In the MIM process, a uniform mixture ofmetallic powder and binders is prepared and injected into a single moldcavity. The binder material provides the proper rheological propertiesnecessary for injection of the metallic material into the mold cavity.Once the part is ejected from the mold, the binder material is removedand the part is then sintered to complete the process. The MIM processis capable of producing single material parts having densities rangingfrom 93 to 99% of theoretical density. Conventional powder metallurgycompaction techniques can form high density single material parts, butcompaction techniques are more limited with respect to the intricategeometries required by some parts. For example, while compaction hasabout a 2 mm tolerance limit, MIM can be used for any geometry having adimension at least equal to the size of the particles comprising themetallic powder, i.e., less than 100 μm. While the MIM process has beenwidely used for formation of single material parts of both simple andcomplex geometry, fields employing composite materials and parts wouldbenefit from the high density and complex geometry obtainable by the MIMprocess.

[0004] In the field of electric machine rotors and generators, themachines are typically constructed of stacked axial laminations orstamped radial laminations. These laminations are configured to providea machine having magnetic, non-magnetic, plastic and/or permanent magnetregions to provide the flux paths and magnetic barriers necessary foroperation of the machines. By way of example, synchronous reluctancerotors formed from stacked axial laminations are structurally weak dueto problems associated both with the fastening and with shifting of thelaminations during operation of their many circumferentiallydiscontinuous components. This results in a drastically lower top speed.Similarly, stamped radial laminations for synchronous reluctance rotorsrequire structural support material at the ends and in the middle ofmagnetic insulation slots. This results in both structural weakness dueto the small slot supports and reduced output power due to magnetic fluxleakage through the slot supports. There are various types of machinesutilizing rotors that require non-magnetic structural support, includingsynchronous reluctance type machines, switched reluctance machines,induction type machines, surface type permanent magnet machines,circumferential type interior permanent magnet machines, and spoke typeinterior permanent magnet machines. Each of these machines comprisingrotor components or rotor sense rings of composite magnetic,non-magnetic, plastic and/or permanent magnet laminations suffer fromthe aforementioned problems.

[0005] While the MIM process has been widely used for formation ofsingle material parts, the field of electric machine rotors andgenerators would benefit from the high density and complex geometryobtainable by the MIM process. Thus, there is a need for the MIM processto be adapted to the production of electric machine rotor and generatorcomposite parts.

SUMMARY OF THE INVENTION

[0006] The present invention provides a method for forming compositemotor parts of two or more dissimilar materials by injection molding. Tothis end, and in accordance with the present invention, two or moredifferent powder materials are injected under heat and pressure intomold cavities and allowed to solidify to form a composite green compact.At least two of the powder materials are metallic-based, and aredifferent from each other. In an example of the present invention, twoor more powder metal materials are each mixed with a binder system toform feedstocks, the feedstocks are melted and concurrently orsequentially injected into a mold and allowed to solidify, and thesolidified composite green compact is then subjected to binder removaland sintering processes. The present invention provides compositeinjection molded parts for machines of the type including permanentmagnet, synchronous reluctance, switched reluctance, and induction.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The accompanying drawings, which are incorporated in andconstitute a part of this specification, illustrate embodiments of theinvention and, together with a general description of the inventiongiven above, and the detailed description given below, serve to explainthe principles of the invention.

[0008]FIG. 1 is a schematic view of the general process steps formanufacturing components by metal injection molding;

[0009]FIG. 2 is a perspective view of an injection molded powder metalpermanent magnet rotor assembly of the present invention having a rotorpositioned on a shaft, the rotor having surface permanent magnets spacedaround a powder metal magnetically conducting segment and separated bypowder metal magnetically non-conducting segments;

[0010]FIG. 3 is a plan view of the rotor assembly of FIG. 2;

[0011]FIG. 4 is a plan view of an alternative embodiment of an injectionmolded powder metal permanent magnet rotor assembly of the presentinvention having surface permanent magnets;

[0012] FIGS. 5-6 are plan views of alternative embodiments of injectionmolded powder metal permanent magnet rotor assemblies of the presentinvention having circumferential type interior permanent magnets;

[0013]FIGS. 7, 7A and 7B are plan views of embodiments of an injectionmolded powder metal permanent magnet rotor assembly of the presentinvention having spoke type interior permanent magnets;

[0014]FIG. 8 is a plan view of an embodiment of an injection moldedpowder metal induction rotor assembly of the present invention having amagnetically conducting segment and a plurality of slots containingconductors enclosed in the slots by magnetically non-conductingsegments;

[0015]FIG. 9 is a plan view of an embodiment of an injection moldedpowder metal synchronous reluctance rotor assembly of the presentinvention having a plurality of arcuate magnetically conducting andnon-conducting segments;

[0016]FIG. 10 is a plan view of an embodiment of an injection moldedpowder metal switched reluctance rotor assembly of the present inventionhaving a magnetically conducting segment and a plurality of magneticallynon-conducting segments; and

[0017] FIGS. 11-13 are schematic views of embodiments of a molding stepin a metal injection molding process in accordance with the presentinvention.

DETAILED DESCRIPTION

[0018] The present invention provides a method for metal injectionmolding of composite rotor parts formed of multiple dissimilarmaterials. Metal injection molding (MIM) is generally used to refer toinjection molding of metallic-based materials; ceramic injection molding(CIM) is generally used to refer to injection molding of ceramic-basedmaterials; and powder injection molding (PIM) is generally used to referto injection molding of either metal-based or ceramic-based materials.For purposes of the present application, MIM, PIM, CIM and injectionmolding are used as synonymous terms for the injection molding of powdermaterials in accordance with the present invention.

[0019] The general process for injection molding is depictedschematically in FIG. 1. A powder material 10 and a binder system 12 areselected for the particular part to be molded. In step 14, the powderand binder are blended or mixed together and granulated or pelletized toprovide the feedstock for the subsequent molding process. The powdermaterial 10 is mixed with the binder system 12 to hold the powdermaterial 10 together prior to injection molding. For the molding process16, the feedstock is melted and then injected into a mold under moderatepressure (i.e., less than about 10,000 psi) and allowed to solidify toform a green compact. The green compact is then ejected from the mold.

[0020] The compact is then subjected to a binder removal process 18,also referred to as debinding or delubing. The debinding step 18typically involves heating the compact to a temperature sufficient tobum off the binder system, leaving a part which is essentially free ofbinder. Thermal debinding typically uses temperatures in the range of100° C.-850° C. The debinding atmosphere may be, for example, nitrogenor nitrogen-based, argon, hydrogen, dissociated ammonia, or mixturesthereof, and may be exothermic or endothermic. Thermal diffusiondebinding may be used in which a reducing atmosphere is provided invacuum. Thermal permeation debinding may be used in which a reducingatmosphere is provided without a vacuum. Thermal wicking debinding maybe used in which the part is packed in a ceramic powder or sand. Thermaloxidation debinding may be used in which debinding is performed in air.Thermal catalytic debinding may be used in which nitric acid is used todepolymerize polyacetals from the binder into formaldehyde, which isburned off at the exhaust of the debinding oven. A first stage solventdebinding may also be used prior to a second stage thermal debinding byone of the above methods. The first stage solvent debinding removes aportion of the binder, usually a wax portion, by exposing the part totemperatures less than about 260° C. Solvent immersion debindinginvolves placing the part in a solvent bath. Solvent vapor debindingplaces the part above a solvent and further uses vapors to remove thebinder. Solvent supercritical debinding is similar to the vapor method,but a pressure is applied to assist and speed up the debinding process.The second stage thermal debinding then removes the remaining portion,typically the backbone binders.

[0021] This binder-free part is then subjected to a sintering process20, which typically includes heating to a temperature sufficiently highto insure densification and homogenization of the molded material,typically in a reducing atmosphere. Pressure could be introduced at thesintering temperature to aid in the densification of the part.

[0022] While metal and ceramic injection molding of a single sourcematerial, including the steps depicted in FIG. 1, is known to thoseskilled in the art of powder metallurgy, the present invention modifiesthe known process to permit injection molding of rotor parts comprisingmore than one material, including soft, hard, and non-ferromagneticmaterials, and filler materials in sense rings. To this end, and inaccordance with the present invention, two or more different feedstocksare prepared, each from a powder material 10 and a binder or carrier 12,such that the mixtures will turn to pastes upon heating. At least two ofthe powder materials 10 are metallic-based, specifically, soft or hardferromagnetic metals and non-ferromagnetic metals, and another powdermaterial 10 may be used that is a filler material, such as a plastic,generally used in rotor sense ring parts. The binder or carrier 12 maybe, for example, a plastic, wax, water or any other suitable bindersystem used for metal injection molding. By way of further example, thebinder system 12 may include a thermoplastic resin, including acrylicpolyethylene, polypropylene, polystyrene, polyvinyl chloride,polyethylene carbonate, polyethylene glycol, and polybutyl methacrylate.Non-restrictive examples of waxes include bees, Japan, montan,synthetic, microcrystalline and paraffin waxes. The binder system mayalso contain, if necessary, plasticizers, such as dioctyl phthalate,diethyl phthalate, di-n-butyl phthalate and diheptyl phthalate.Generally, a feedstock for metal injection molding will contain a bindersystem 12 in an amount up to about 70% by volume, with about 30-50%being most common.

[0023] As with the general method described above, each powder/bindermixture is formed into pellets, small balls or granules to provide thefeedstocks for the subsequent molding process. Each feedstock is heatedto a temperature sufficient to allow the mixture's injection through aninjection unit. While although some materials may be injected attemperatures as low as room temperature, the mixtures are typicallyheated to a temperature between about 85° F. (29° C.) to about 385° F.(196° C.). The melted feedstocks are then injected into a mold, eithersequentially or concurrently. The melting and injection are typicallyconducted in an inert gas atmosphere, such as argon, nitrogen, hydrogenand helium. The rates of injection are not critical to the invention,and can be determined by one skilled in the art in accordance with thecompositions of each feedstock. Different injection units areadvantageously used for each feedstock to avoid cross-contaminationwhere such contamination should be avoided.

[0024] The mold is designed according to the pattern desired for thecomposite rotor part. Molds for metal injection molding areadvantageously comprised of a hard material, such as steel, so as towithstand abrasion from the powder materials. Sliding cores, ejectors,and other moving components can be incorporated in the mold whennecessary to form the different material regions of the composite part.Thus, the mold is created to have two or more cavities into which thefeedstocks are injected. The cavities correspond to the particulardesign needed for the desired machine type. The overall mold isgenerally cylindrical, which corresponds to the general shape of a rotorcomponent for mounting on a shaft to form a rotor assembly of a rotormachine. Rotor components and sense rings have part geometries andmaterial boundaries that are often intricate, such that the tighttolerances achievable in injection molding can enable manufacture of asuperior, high density intricate rotor part.

[0025] Exemplary embodiments will now be described for various types ofrotor components that may be manufactured in accordance with the presentinvention. These embodiments are by no means exhaustive. Numerousvariations exist in rotor design, and such variations are within theordinary skill of one in the art.

[0026] The present invention provides an injection molded compositepowder metal rotor component for use in a surface permanent magnetmachine, the assembly having an inner annular magnetically conductingsegment of injection molded soft ferromagnetic powder metal and an outerannular permanent magnet segment of alternating polarity permanentmagnets. The permanent magnet segment may be a continuous magnet ringwith regions of alternating polarity around the circumference of thecomponent or may be discrete permanent magnets separated from each otherby spaces or by non-ferromagnetic injection molded powder metalsegments. The permanent magnets may be prefabricated discrete magnets ora full magnet ring affixed onto the inner annular segment or may beinjection molded hard ferromagnetic powder metal. The injection moldedcomponent is mounted on a shaft to form a powder metal rotor assembly. Apermanent magnet machine incorporating the powder metal rotor assemblyof the present invention is simpler to manufacture and at a lower costthan prior surface permanent magnet rotors and exhibits increasedefficiency by reducing flux leakage.

[0027] The present invention also provides a rotor sense ring having aconfiguration similar to the rotor component, but having a plastic orother filler material in place of the inner annular magneticallyconducting segment.

[0028] With reference to the Figures, FIGS. 2 and 3 depict inperspective view and plan view, respectively, a powder metal surfacepermanent magnet rotor assembly 30 of the present invention having aninjection molded powder metal composite component 32 mounted on a shaft34, the component 32 having an inner annular magnetically conductingsegment 36 and an outer annular permanent magnet segment 38 comprising aplurality of alternating polarity permanent magnets 40. The permanentmagnets 40 and inner annular segment 36 are formed by injection moldinghard ferromagnetic powder metal and soft ferromagnetic powder metal,respectively. In the particular embodiment of FIGS. 2 and 3, thepermanent magnet segment 38 includes magnetically non-conductingsegments 42 separating the permanent magnets 40. The non-conductingsegments 42, which are formed by injection molding non-ferromagneticpowder metal, provide insulation that directs the magnetic flux from onepermanent magnet 40 to the next alternating polarity permanent magnet40. Further in this embodiment, the hard, soft and non-ferromagneticpowder metals may be injection molded sequentially or concurrently toform the permanent magnets 40, the inner annular magnetically conductingsegment 36 and the non-conducting segments 42, respectively. In anotherembodiment, a plastic powder or filler powder material is injectionmolded to form a non-conductive inner annular segment 36N in place ofthe magnetically conducting segment 36 to thus form a rotor sense ring.

[0029] In FIG. 4, the composite injection molded powder metal component32 is similar to that depicted in FIGS. 2 and 3, but the component 32further includes an inner annular non-conducting insert 44 adjacent theinterior surface 46 of the component 32 in addition to the inner annularmagnetically conducting segment 36. The insert 44 blocks magnetic fluxfrom being channeled toward the shaft 34. FIG. 4 also depicts a lowernumber of larger permanent magnets 40 separated by thickernon-conducting segments 42 as compared to FIGS. 2 and 3. It should beunderstood, however, that permanent magnet segment 38 may comprise thepermanent magnets 40 only, with no separating non-conducting segments42.

[0030] The present invention further provides an injection moldedcomposite powder metal rotor component for use in a circumferential typeinterior permanent magnet machine, the component having an optionalinner magnetically conducting segment and an outer permanent magnetsegment. This outer segment includes alternating polarity permanentmagnets separated in between by magnetically non-conducting barriersegments. The permanent magnets are also circumferentially embedded byradially outer magnetically conducting segments optionally havingmagnetically non-conducting bridge segments extending from the permanentmagnets to an outer surface of the component. The outer and optionalinner magnetically conducting segments comprise injection molded softferromagnetic powder metal. The magnetically non-conducting barrier andoptional bridge segments comprise injection molded non-ferromagneticpowder metal. The permanent magnets comprise injection molded hardferromagnetic powder metal, or may be prefabricated magnets affixed toadjacent segments. The hard, soft and non-ferromagnetic powder metalsmay be injection molded concurrently or sequentially. The injectionmolded component is mounted on a shaft to form a powder metal rotorassembly. A circumferential type interior permanent magnet machineincorporating the powder metal rotor assembly of the present inventionexhibits increased power and speed capabilities, lower flux leakage, andmay be produced at a lower cost.

[0031]FIGS. 5 and 6 depict in plan view alternative powder metalcircumferential type interior permanent magnet rotor assemblies 50 ofthe present invention having an injection molded powder metal compositecomponent 52 mounted on a shaft 54, the component 52 having an innerannular magnetically conducting segment 56 and an outer annularpermanent magnet segment 58 comprising a plurality of alternatingpolarity circumferentially extending permanent magnets 60. The permanentmagnet segment 58 includes magnetically non-conducting barrier segments62 separating the permanent magnets 60. The non-conducting barriersegments 62 provide insulation that directs the magnetic flux from onepermanent magnet 60 to the next alternating polarity permanent magnet60. The permanent magnet segment 58 further includes a radially outermagnetically conducting segment 64 adjacent each permanent magnet 60that embeds the permanent magnet 60 in the component 52. Each radiallyouter magnetically conducting segment 64 further includes anintermediate magnetically non-conducting bridge segment 66 that extendsradially from a respective permanent magnet 60 to an outercircumferential surface 68 of component 52. Each bridge segment 66essentially cuts its respective radially outer magnetically conductingsegment 64 in two. It should be understood, however, that theintermediate bridge segments 66 may be omitted from the component. Thenon-conducting segments 62 provide insulation that directs the magneticflux from one permanent magnet 60 to the next alternating polaritypermanent magnet 60. FIG. 5 includes a magnetically non-conductinginsert 70 in the inner annular segment 56. Insert 70 has an essentiallystar-shaped configuration and extends from the interior surface 72 ofthe component 52 into tip portions 70 a or 70 b that terminate at (70 a)or near (70 b) a respective permanent magnet 60 in the outer annularpermanent magnet segment 58. As can be seen, the magnetically conductingportions 56 a of the inner annular magnetically conducting segment 56direct magnetic flux from one permanent magnet 60 to the nextalternating polarity permanent magnet 60. The insert 70 also blocksmagnetic flux from being channeled into the shaft 54. FIG. 6 is similarto FIG. 5, but the component 52 includes an inner annular non-conductinginsert 74 adjacent the interior surface 72 of the component 52. Theinsert 74 likewise blocks magnetic flux from being channeled into theshaft 54.

[0032] Alternatively, component 52 can be made without the inner annularmagnetically conducting segment 56. Thus, component 52 would comprise aring 58 of alternating polarity circumferentially extending permanentmagnets 60 separated by magnetically non-conducting barrier segments 62and partially embedded by radially outer magnetically conductingsegments 64, with or without bridge segments 66. Component 52 is thenassembled onto a sleeve or cylinder, with or without a separate wroughtor machined shaft.

[0033] The present invention provides a composite powder metal rotorassembly for a spoke type interior permanent magnet machine, thecomponent having an optional inner annular non-ferromagnetic powdermetal segment and an outer annular permanent magnet segment with aplurality of alternating polarity, radially extending permanent magnetsseparated by magnetically conducting segments and capped by magneticallynon-conducting segments. The outer and optional inner magneticallynon-conducting segments comprise injection molded non-ferromagneticpowder metal. Thus, both ends of the permanent magnets are bordered by astructurally robust non-ferromagnetic powder metal material to therebyminimize flux leakage around the magnet ends. The magneticallyconducting segments comprise injection molded soft ferromagnetic powdermetal. The permanent magnets comprise injection molded hardferromagnetic powder metal, or may be prefabricated magnets affixed toadjacent segments. The hard, soft and non-ferromagnetic powder metalsmay be injection molded concurrently or sequentially. The injectionmolded component is mounted on a shaft to form a powder metal rotorassembly. A spoke type interior permanent magnet machine incorporatingthe powder metal rotor assembly of the present invention exhibits fluxconcentration, minimal flux leakage and permits the motor to producemore power than a circumferential interior permanent magnet motor or toproduce the same power using less powerful and less expensive magnets,and may be produced at a lower overall cost.

[0034]FIG. 7 depicts in plan view a powder metal spoke type interiorpermanent magnet rotor assembly 80 of the present invention having aninjection molded powder metal composite component 82 mounted on a shaft84, the component 82 having an inner annular magnetically non-conductingsegment 86 and an outer annular permanent magnet segment 88 comprising aplurality of alternating polarity permanent magnets 90 separated bymagnetically conducting segments 92. The conducting segments 92 directthe magnetic flux from one permanent magnet 90 to the next alternatingpolarity permanent magnet 90. The permanent magnet segment 88 furtherincludes a radially outer magnetically non-conducting segment 94adjacent each permanent magnet 90 that embeds the permanent magnet 90 inthe component 82.

[0035] Alternatively, a spoke type rotor component 82 can be madewithout the inner annular magnetically non-conducting segment 86, asdepicted in FIGS. 7A-7B. Thus, the component 82 comprises an outerannular permanent magnet segment 88 having a plurality of alternatingpolarity permanent magnets 90 separated by magnetically conductingsegments 92 and radially embedded by magnetically non-conductingsegments 94. The magnetically conducting segments 92 can be made with acontinuous inner ring 92 a adjacent the interior surface 96 of thecomponent 82, as shown in FIG. 7B. The inner ring 92 a can be minimizedor eliminated by machining. Magnets 90 can be prefabricated and affixedinto the component 82 or can be hard ferromagnetic powder metal injectedconcurrently or sequentially with the other powder metals. Component 82can be assembled onto a sleeve or cylinder (not shown), with or withouta separate wrought or machined shaft (not shown).

[0036] The present invention provides an injection molded compositepowder metal rotor component for use in an induction machine, thecomponent comprising a magnetically conducting segment with spacedaxially extending slots around the exterior surface of the component forreceiving a plurality of conductors. A magnetically non-conductingsegment encloses each slot opening adjacent the exterior surface of thecomponent. The conductors may be cast into the slots of the compositecomponents or may be prefabricated bars inserted into the slots. Themagnetically conducting segment comprises injection molded softferromagnetic powder metal. The magnetically non-conducting segmentscomprise injection molded non-ferromagnetic powder metal. The soft andnon-ferromagnetic powder metals may be injection molded concurrently orsequentially. The injection molded component is mounted on a shaft toform a powder metal rotor assembly. An induction machine incorporatingthe powder metal rotor assembly of the present invention can obtain highspeeds with low flux leakage, and yet may be produced at a lower cost.

[0037]FIG. 8 depicts in plan view a powder metal induction rotorassembly 100 of the present invention having an injection molded powdermetal composite component 102 mounted on a shaft 104, the component 102having a magnetically conducting segment 106 and a plurality of slots orslot openings 108 extending along the axial length of the component 102.Within each slot 108 is a conductor 110 enclosed by a magneticallynon-conducting segment 112. Thus, each slot 108 receives a conductor 110in a radially inner portion of the slot 108, and a radially outerportion of the slot 108 comprises the non-conducting segment 112 suchthat the conductors 110 are embedded within the rotor assembly 100. Ateach end of the rotor assembly 100 is an end ring 114, which end rings114 are integral with the conductors 110. In one embodiment of thepresent invention, the end rings 114 are cast together with theconductors 110. In an alternative embodiment of the present invention,the conductors 110 are first inserted into the slot openings 108, andthen the end rings 114 are placed at either end of the assembly 100 andthe conductors 110 are affixed to the end rings 114 by any suitablemeans. As may be appreciated by one skilled in the art, the end rings114 may include molded fan blades (not shown).

[0038] The present invention provides an injection molded compositepowder metal rotor component for use in a synchronous reluctancemachine, the component having alternating magnetically conducting andmagnetically non-conducting segments. The magnetically conductingsegments comprise injection molded soft ferromagnetic powder metal. Themagnetically non-conducting segments comprise injection moldednon-ferromagnetic powder metal. The soft and non-ferromagnetic powdermetals may be injection molded concurrently or sequentially. Theinjection molded component is mounted on a shaft to form a powder metalrotor assembly. A synchronous reluctance machine incorporating thepowder metal rotor assembly of the present invention exhibits powerdensity and efficiency comparable to induction motors and improved highspeed rotating capability, yet may be produced at a lower cost.

[0039]FIG. 9 depicts in plan view a powder metal synchronous reluctancerotor assembly 120 of the present invention having an injection moldedpowder metal composite component 122 mounted on a shaft 124, thecomponent 122 having a plurality of alternating magnetically conductingsegments 126 and non-conducting segments 128. In the particularembodiment of FIG. 9, the segment 126 a adjacent the interior surface130 of the component 122 is a conducting segment 126. This segment 126essentially forms four equiangular spaced, radially extending armportions 126 a-d that define axially extending channels there between.Within those channels are alternating layers of magneticallynon-conducting segments 128 and magnetically conducting segments 126. Itshould be understood, however, that the segment adjacent the interiorsurface 130 may be non-conducting, with alternating layers ofmagnetically conducting segments 126 and magnetically non-conductingsegments 128 in the channels. A variety of other magnetic configurationsare known and well within the skill of one in the art.

[0040] The present invention provides an injection molded compositepowder metal rotor component for use in a switched or variablereluctance machine, the component having a magnetically conductingsegment and a plurality of magnetically non-conducting segments. Themagnetically conducting segment comprises injection molded softferromagnetic powder metal. The magnetically non-conducting segmentscomprise injection molded non-ferromagnetic powder metal. The soft andnon-ferromagnetic powder metals may be injection molded concurrently orsequentially. The injection molded component is mounted on a shaft toform a powder metal rotor assembly. A switched reluctance machineincorporating the powder metal rotor assembly of the present inventionexhibits low windage losses as compared to assemblies comprising stampedlaminations.

[0041]FIG. 10 depicts in plan view a powder metal switched reluctancerotor assembly 140 of the present invention having an injection moldedcomposite powder metal component 142 mounted on a shaft 144, thecomponent having a magnetically conducting segment 146 that has a yokeportion 146 a and a plurality of equiangular spaced, radially extendingteeth 146 b defining channels there between, and magneticallynon-conducting segments 148 in the channels between the teeth 146 b. Thenon-conducting segments 148 function to cut down on windage losses.

[0042] In an embodiment of the present invention, the soft ferromagneticpowder metal used in the above-described components is nickel, iron,cobalt or an alloy thereof. In another embodiment of the presentinvention, this soft ferromagnetic metal is a low carbon steel or a highpurity iron powder with a minor addition of phosphorus, such as coveredby MPIF (Metal Powder Industry Federation) Standard 35 F-0000, whichcontains approximately 0.27% phosphorus. In general, AISI 400 seriesstainless steels are magnetically conducting, and may be used in thepresent invention.

[0043] In an embodiment of the present invention, the non-ferromagneticpowder metal used in the above-described components is austeniticstainless steel, such as SS316. In general, the AISI 300 seriesstainless steels are non-magnetic and may be used in the presentinvention. Also, the AISI 8000 series steels are non-magnetic and may beused.

[0044] In an embodiment of the present invention, the soft ferromagneticmetal and the non-ferromagnetic metal are chosen so as to have similardensities and sintering temperatures, and are approximately of the samestrength, such that upon injection and sintering, the materials behavein a similar fashion. In an embodiment of the present invention, thesoft ferromagnetic powder metal is Fe-0.27%P and the non-ferromagneticpowder metal is SS316.

[0045] In an embodiment of the present invention, the hard ferromagneticpowder metal used in the above-described components for the permanentmagnets is ferrite or rare earth metals.

[0046] Referring further to the Figures to illustrate the method of thepresent invention, FIG. 11 depicts one embodiment of the presentinvention utilizing a single molding machine (not shown) having threeinjection units 170, 172, 174 for filling a single mold 176 with threedissimilar materials 177, 178, 179, specifically hard ferromagnetic,soft ferromagnetic and non-ferromagnetic powder metals. As stated above,the mold is generally cylindrically shaped, which corresponds to thegeneral shape of a rotor assembly. Depending on the pattern of the partto be molded, the injection units 170, 172, 174 may be stationary duringthe injection process, or may be rotated or moved in any desired patternto inject the three materials 177, 178, 179 concurrently or sequentiallyto form the composite part. Although three different materials aredescribed, it should be understood that the present invention and theembodiment of FIG. 11 have application for forming parts made of two ormore dissimilar materials, in any composite rotor or rotor sense ringpattern. Once all of the materials have been injected and have beenallowed to solidify, the mold 176 is opened and the part ejectedtherefrom. The part may then be subjected to known binder removal andsintering processes to form a final high density composite part.

[0047]FIG. 12 depicts an alternative embodiment of the method of thepresent invention. In this embodiment, multiple molds 180, 182, 184 areused to inject each of the dissimilar materials 177, 178, 179independently or sequentially. A first material or melted feedstock 177is injected into one or more cavities 186 in the first mold 180 by aninjection unit 181 to form the proper shape. For purposes of simplicityof depiction, each mold 180, 182, 184 shown in FIG. 12 has threecavities 186, 188, 190, each cavity receiving a different material, forforming a three-material composite part. It is to be understood,however, that a first feedstock 177 may be injected into one cavity 186or multiple distinct cavities, and a second feedstock 178 different thanthe first feedstock 177 may be injected into one cavity 188 or multipledistinct cavities, and so on, to form a composite part of two or morematerials in any desired rotor or rotor sense ring pattern. After thefirst material 177 is injected, and allowed to solidify, the partiallyformed part 192 is then ejected and placed into a second mold 182. Asecond dissimilar material 178 is injected into another cavity 188 inmold 182, either by a second injection unit 183 from the same singlemachine (not shown), or by an injection unit 183 of a second machine(not shown). After the second material 178 is allowed to solidify, thepartially formed part 194 is removed and placed into a third mold 184for injection of a third dissimilar material 179 by a third injectionunit 185. After the third material 179 is allowed to solidify, thecomplete molded part 196, or green compact, is ejected from the thirdmold 184, and the compact 196 is debound and sintered. The embodimentshown and described with reference to FIG. 12 may be used to formcomposite components having two or more dissimilar materials, in anycomposite rotor or rotor sense ring pattern.

[0048]FIG. 13 depicts yet another embodiment of the method of thepresent invention using a progressive or sequential molding processwhere the rotor part to be formed remains in a single mold. In thisprocess, a bottom or ejector mold half 200 is shuttled from oneinjection unit 202 to another 204, 206 through a series of mating topmold halves 208, 210, 212 that contain the required runner system toinject the multiple dissimilar materials into the mold cavities 220,222, 224 to form the desired composite rotor or rotor sense ringpattern. Removable cores 214, 216 may be used in conjunction with thetop mold halves. Other runner system and core designs are within theordinary skill of one in the art, and the invention should in no way belimited to the particular designs depicted herein. More specifically,the bottom mold half 200 is placed under a first injection unit 202 andfirst top mold half 208 for injection of a first material or meltedfeedstock 177 into one or more cavities 220 in the bottom mold half 200.Again for simplicity of depiction, the mold 200 shown in FIG. 13 hasthree cavities 220, 222, 224 formed by placement of the cores 214, 216,each cavity receiving a different material, for forming a three-materialcomposite part. The bottom mold half 200 is then moved to a second topmold half 210 and second injection unit 204, which is either a secondinjection unit 204 in a single molding machine (not shown), or theinjection unit 204 of a different machine (not shown). A seconddissimilar material 178 is then injected into one or more cavities 222in the bottom mold half 200. The bottom mold half 200 is then moved toyet a third top mold half 212 and third injection unit 206 for injectionof a third dissimilar material 179 into one or more cavities 224 of thebottom mold half 200. After the materials have all solidified, thecomplete molded part 226, or green compact, is ejected from the bottommold half 200, and the compact 226 is debound and sintered. Theembodiment shown and described with reference to FIG. 13 may be used toform composite components having two or more dissimilar materials, inany composite rotor or rotor sense ring pattern.

[0049] It should be understood that there is no limit to the number ofcavities or geometry of the cavities in a mold for forming a compositerotor or rotor sense ring part, nor is there a limit to the number ofdissimilar materials that may ultimately form the composite part.Sliding cores, removable cores, ejectors, and other moving componentscan be incorporated in one or more of the molds used in practicing thepresent invention whenever necessary to form the composite part.Although alternative embodiments for practicing the invention have beendescribed, the invention should in no way be limited to the particularmold designs or methods described. The present invention provides amethod for forming composite rotor parts of multiple dissimilarmaterials by metal injection molding, regardless of the part or moldgeometry.

[0050] It should be further understood that dissimilar materials behavedifferently during injection and solidification, such that thedissimilar materials should be selected or manipulated to have similarshrinkage ratios, as well as compatible binder removal and sinteringcycles to minimize defects in the final product, where such defectswould render the part unacceptable for its purpose. By way of exampleonly, particle size, particle size distribution, particle shape andpurity of the powder material can be selected or manipulated to affectsuch properties or parameters as apparent density, green strength,compressibility, sintering time and sintering temperature. The amountand type of binder mixed with each powder material may also affectvarious properties of the feedstock, green compact and sinteredcomponent, and various process parameters. The method for forming thepowder materials, including mechanical, chemical, electrochemical andatomizing processes, also can affect the performance of the powdermaterial during the injection molding process.

[0051] Following ejection of the parts from the mold, the molded partsare debound to remove the binder material. Debinding processes are wellknown to those skilled in the art of powder metallurgy, and aredescribed in detail above. By way of example, one general practice inthe industry for thermal debinding includes heating to a temperature inthe range of about 100° C. to about 850° C., typically about 760° C.(1400° F.), and holding at that temperature for less than about 6 hours,typically about 2 hours, to burn off the binder material.

[0052] The composite part is then subjected to a sintering process,which is also well known to those skilled in art of powder metallurgy.The sintering step typically comprises raising the temperature from thedebinding step to a higher temperature in the range of about 1742° F.(950° C.) to about 3272° F. (1800° C.), typically about 2050° F. (1121°C.), and holding at that temperature for less than about 6 hours,typically about 2 hours. Sintering achieves densification chiefly byformation of particle-to-particle binding, thereby forming ahigh-density, coherent mass of two or more materials with clear,well-defined boundaries there between. Densities approaching fulltheoretical density are possible in the composite parts of the presentinvention, generally up to about 99% of theoretical.

[0053] The debinding and sintering processes may be conducted separatelywith intermediate cooling in between, or may be separate consecutivesteps in a continuous process. It should be understood that thedebinding and sintering times and temperatures may be adjusted asnecessary, which adjustment is well within the skill of one in the art.For example, different binder systems may warrant differing debindingprocesses, temperatures, and time cycles, and different powder materialsmay warrant differing sintering temperature and time cycles. Thedebinding and sintering operations may be performed in a vacuum furnace,and the furnace may be filled with an argon or other reducingatmosphere. Alternatively, the processes may be performed in acontinuous belt furnace, which is generally provided with ahydrogen/nitrogen atmosphere such as 75% H₂/25% N₂. Other types offurnaces and furnace atmospheres may be used within the scope of thepresent invention as determined by one skilled in the art.

[0054] While the present invention has been illustrated by thedescription of embodiments thereof, and while the embodiments have beendescribed in considerable detail, they are not intended to restrict orin any way limit the scope of the appended claims to such detail.Additional advantages and modifications will readily appear to thoseskilled in the art. The invention in its broader aspects is thereforenot limited to the specific details, representative apparatus andmethods and illustrative examples shown and described. Accordingly,departures may be made from such details without departing from thescope or spirit of applicant's general inventive concept.

What is claimed is:
 1. A method for injection molding composite rotorcomponents, the method comprising: injecting a ferromagnetic powdermaterial from a first injection unit under heat and pressure into afirst mold cavity, and allowing the ferromagnetic material to solidify;injecting a non-ferromagnetic powder material from a second injectionunit under heat and pressure into a second mold cavity adjacent theferromagnetic material, and allowing the non-ferromagnetic material tosolidify to thereby produce a composite injection molded rotorcomponent.
 2. The method of claim 1, wherein the ferromagnetic powdermaterial is soft ferromagnetic powder metal or hard ferromagnetic powdermetal.
 3. The method of claim 1, wherein the ferromagnetic powdermaterial is a soft ferromagnetic powder metal selected from the groupconsisting of Ni, Fe, Co and alloys thereof.
 4. The method of claim 1,wherein the ferromagnetic powder material is a soft ferromagnetic highpurity iron powder with a minor addition of phosphorus.
 5. The method ofclaim 1, wherein the non-ferromagnetic powder material is an austeniticstainless steel.
 6. The method of claim 1, wherein the non-ferromagneticpowder material is an AISI 8000 series steel.
 7. The method of claim 1,wherein the ferromagnetic and non-ferromagnetic powder materials areeach combined with a binder prior to injecting.
 8. The method of claim7, further comprising the steps of: ejecting the composite componentfrom the mold; subjecting the composite component to debinding toprovide a composite part which is essentially free of binder; andsintering the composite part.
 9. The method of claim 1, wherein thefirst and second injection units are part of a single injection moldingmachine, with each unit positioned to inject the respective powdermaterial into the respective first and second mold cavity of a singlemold.
 10. The method of claim 1, wherein the first and second injectionunits are part of separate injection molding machines, and a single moldhaving the first and second mold cavities is transferred sequentially toeach machine for injecting the respective powder material into therespective first and second mold cavity.
 11. The method of claim 1,wherein the first mold cavity is in a first mold and the second moldcavity is in a second mold, and wherein the ferromagnetic powdermaterial is injected into and solidified in the first mold cavity, thenremoved and inserted into the second mold, and the non-ferromagneticpowder material is injected into and solidified in the second moldcavity.
 12. The method of claim 1, further comprising injecting one ormore additional powder materials into one or more additional moldcavities, each additional powder material having a different compositionthan the ferromagnetic and non-ferromagnetic powder materials, to form acomposite injection molded component of at least three or more differentmaterials.
 13. The method of claim 12, wherein the ferromagnetic powdermaterial is a soft ferromagnetic metal and one additional powdermaterial is a hard ferromagnetic powder metal thereby forming apermanent magnet rotor component.
 14. The method of claim 12, whereinthe ferromagnetic powder material is a hard ferromagnetic metal and oneadditional powder material is a plastic filler material thereby forminga rotor sense ring component.
 15. The method of claim 1, wherein thenon-ferromagnetic powder material is injected concurrently with theferromagnetic powder material.
 16. The method of claim 1, wherein thenon-ferromagnetic powder material is injected after the ferromagneticpowder material is allowed to solidify.
 17. The method of claim 1further comprising mounting the composite component on a shaft to form apowder metal rotor assembly.
 18. A method for injection moldingcomposite rotor components, comprising the steps of: preparing at leasttwo different feedstocks, each feedstock comprising a mixture of apowder material and a binder, the powder materials being selected fromthe group consisting of hard ferromagnetic, soft ferromagnetic andnon-ferromagnetic; feeding each feedstock to a respective injectionunit; melting the feedstocks; and molding the feedstocks into acomposite compact of desired shape comprising at least two differentmaterials by injecting melted feedstock from each injection unit underheat and pressure into a respective portion of a mold, and allowing thefeedstocks to solidify.
 19. The method of claim 18, further comprisingthe steps of: ejecting the compact from the mold; subjecting the compactto debinding to provide a part which is essentially free of binder; andsintering the part.
 20. The method of claim 18, wherein each feedstockis injected into the respective portion of a single mold to form thecomposite compact.
 21. The method of claim 20, wherein the injectionunits form a single injection molding machine, with each unit positionedto inject feedstock into the respective portion of the single mold. 22.The method of claim 21, wherein all feedstocks are injectedconcurrently.
 23. The method of claim 21, wherein the feedstocks areinjected sequentially.
 24. The method of claim 20, wherein eachinjection unit is part of a separate injection molding machine, and thesingle mold is transferred sequentially to each machine for injectingthe respective feedstock into the respective portion of the single mold.25. The method of claim 18, comprising repeating the steps of injectingone melted feedstock into the respective portion of the mold andallowing the feedstock to solidify, followed by transferring thesolidified feedstock to another mold, until each feedstock has beeninjected, to thereby form the composite compact.
 26. The method of claim18, wherein the soft ferromagnetic powder metal is Ni, Fe, Co or analloy thereof.
 27. The method of claim 18, wherein the softferromagnetic powder metal is high purity iron powder with a minoraddition of phosphorus.
 28. The method of claim 18, wherein thenon-ferromagnetic powder metal is an austenitic stainless steel.
 29. Themethod of claim 18, wherein the non-ferromagnetic powder metal is anAISI 8000 series steel.
 30. The method of claim 18, further comprisingmounting the composite component on a shaft to form a powder metal rotorassembly.
 31. The method of claim 18, wherein a first feedstock is asoft ferromagnetic powder metal injected into an inner annular region ofa cylinder-shaped mold, and a second feedstock is a non-ferromagneticpowder metal injected into discrete regions within an outer annularregion of the mold so as to leave spaces between each discrete region,and a third feedstock is a hard ferromagnetic powder metal injected intothe spaces between the discrete regions of the outer annular region ofthe mold, whereby upon solidifying a composite powder metal componentfor a surface permanent magnet machine is formed having an inner annularmagnetically conducting segment and an outer annular segment of aplurality of alternating polarity permanent magnets separated bymagnetically non-conducting segments.
 32. The method of claim 18,wherein a first feedstock is a soft ferromagnetic powder metal injectedinto an inner annular region of a cylinder-shaped mold, and a secondfeedstock is a hard ferromagnetic powder metal injected into an outerannular region of the mold, whereby upon solidifying a composite powdermetal component for a surface permanent magnet machine is formed havingan inner annular magnetically conducting segment and an outer annularpermanent magnet ring.
 33. The method of claim 18, wherein a firstfeedstock is a soft ferromagnetic powder metal injected into an innerannular region of a cylinder-shaped mold, and a second feedstock is anon-ferromagnetic powder metal injected into discrete regions within anouter annular region of the mold so as to leave spaces between eachdiscrete region, whereby upon solidifying a composite powder metalcomponent for a surface permanent magnet machine is formed having aninner annular magnetically conducting segment and an outer annularsegment of a plurality of spaces separated by magneticallynon-conducting segments, the method further comprising affixingpre-fabricated magnets in the spaces in an arrangement of alternatingpolarity.
 34. The method of claim 18, wherein a first feedstock is anon-ferromagnetic powder metal injected into discrete regions within anannular region of the mold so as to leave spaces between each discreteregion, and a second feedstock is a hard ferromagnetic powder metalinjected into the spaces between the discrete regions of the annularregion of the mold, whereby upon solidifying a composite powder metalcomponent for a surface permanent magnet machine is formed having anannular segment of a plurality of alternating polarity permanent magnetsseparated by magnetically non-conducting segments.
 35. The method ofclaim 18, wherein a first feedstock is a soft ferromagnetic powder metalinjected into an inner annular region of a cylinder-shaped mold, asecond feedstock is a non-ferromagnetic powder metal injected intodiscrete first regions within an outer annular region of the mold so asto leave spaces between each discrete first region, and wherein thefirst feedstock is further injected into two discrete second regionsbetween the first regions so as to leave a radially innercircumferentially extending space and a radially extending space betweenthe two discrete regions, and wherein the second feedstock is furtherinjected into the radially extending spaces, and a third feedstock is ahard ferromagnetic powder metal injected into the radially innercircumferentially extending spaces between the discrete first regions ofthe mold, whereby a composite powder metal component for acircumferential type interior permanent magnet machine is formed havingan inner annular magnetically conducting segment and an outer permanentmagnet segment of a plurality of alternating polarity permanent magnetsseparated by magnetically non-conducting barrier segments and radiallyembedded by magnetically conducting segments with intermediatemagnetically non-conducting bridge segments.
 36. The method of claim 18,wherein a first feedstock is a soft ferromagnetic powder metal injectedinto an inner annular region of a cylinder-shaped mold, a secondfeedstock is a non-ferromagnetic powder metal injected into discretefirst regions within an outer annular region of the mold so as to leavespaces between each discrete first region, and wherein the firstfeedstock is further injected into two discrete second regions betweenthe first regions so as to leave a radially inner circumferentiallyextending space and a radially extending space between the two discreteregions, and wherein the second feedstock is further injected into theradially extending spaces, whereby a composite powder metal componentfor a circumferential type interior permanent magnet machine is formedhaving an inner annular magnetically conducting segment and an outerpermanent magnet segment of a plurality of circumferentially extendingspaces separated by magnetically non-conducting barrier segments andradially embedded by magnetically conducting segments with intermediatemagnetically non-conducting bridge segments, the method furthercomprising affixing pre-fabricated magnets in the circumferentiallyextending spaces in an arrangement of alternating polarity.
 37. Themethod of claim 18, wherein a first feedstock is a non-ferromagneticpowder metal injected into discrete first regions within an annularregion of the mold so as to leave spaces between each discrete firstregion, and wherein a second feedstock is a soft ferromagnetic powdermetal injected into two discrete second regions between the firstregions so as to leave a radially inner circumferentially extendingspace and a radially extending space between the two discrete regions,and wherein the first feedstock is further injected into the radiallyextending spaces, and a third feedstock is a hard ferromagnetic powdermetal injected into the radially inner circumferentially extendingspaces between the discrete first regions of the mold, whereby acomposite powder metal component for a circumferential type interiorpermanent magnet machine is formed having an outer permanent magnetsegment of a plurality of alternating polarity permanent magnetsseparated by magnetically non-conducting barrier segments and radiallyembedded by magnetically conducting segments with intermediatemagnetically non-conducting bridge segments.
 38. The method of claim 18,wherein a first feedstock is a non-ferromagnetic powder metal injectedinto an inner annular region of a cylinder-shaped mold, a secondfeedstock is a soft ferromagnetic powder metal injected into discretefirst regions within an outer annular region of the mold so as to leavespaces between each discrete first region, and wherein the firstfeedstock is further injected into discrete radially outer secondregions between the first regions so as to leave a radially innerradially extending space between each of the adjacent first regions, anda third feedstock is a hard ferromagnetic powder metal injected into theradially extending spaces between the discrete first regions of themold, whereby a composite powder metal component for a spoke typeinterior permanent magnet machine is formed having an inner annularmagnetically non-conducting segment and an outer annular segment of aplurality of alternating polarity permanent magnets separated bymagnetically conducting segments and embedded by magneticallynon-conducting segments.
 39. The method of claim 18, wherein a firstfeedstock is a non-ferromagnetic powder metal injected into an innerannular region of a cylinder-shaped mold, a second feedstock is a softferromagnetic powder metal injected into discrete first regions withinan outer annular region of the mold so as to leave spaces between eachdiscrete first region, and wherein the first feedstock is furtherinjected into discrete radially outer second regions between the firstregions so as to leave a radially inner radially extending space betweeneach of the adjacent first regions, whereby a composite powder metalcomponent for a spoke type interior permanent magnet machine is formedhaving an inner annular magnetically non-conducting segment and an outerannular segment of a plurality of radially extending spaces separated bymagnetically conducting segments and embedded by magneticallynon-conducting segments, the method further comprising affixingpre-fabricated magnets in the radially extending spaces in anarrangement of alternating polarity.
 40. The method of claim 18, whereina first feedstock is a soft ferromagnetic powder metal injected intodiscrete first regions within an annular region of the mold so as toleave spaces between each discrete first region, and wherein a secondfeedstock is a non-ferromagnetic powder metal injected into discreteradially outer second regions between the first regions so as to leave aradially inner radially extending space between each of the adjacentfirst regions, and a third feedstock is a hard ferromagnetic powdermetal injected into the radially extending spaces between the discretefirst regions of the mold, whereby a composite powder metal componentfor a spoke type interior permanent magnet machine is formed having anannular segment of a plurality of alternating polarity permanent magnetsseparated by magnetically conducting segments and embedded bymagnetically non-conducting segments.
 41. The method of claim 18,wherein a first feedstock is a soft ferromagnetic powder metal injectedinto a first region of a cylinder-shaped mold to form a pattern of aplurality of equally spaced axially extending slots adjacent an exteriorcircumferential surface of the mold, and a second feedstock is anon-ferromagnetic powder metal injected into a plurality of discretesecond regions of the mold in a radially outer portion of each slotadjacent the exterior circumferential surface of the mold, whereby acomposite powder metal component for an induction machine is formedhaving a magnetically conducting segment and a plurality of magneticallynon-conducting segments enclosing slot openings.
 42. The method of claim18, wherein a first feedstock is a soft ferromagnetic powder metalinjected into one or more discrete first regions in a cylinder-shapedmold, and a second feedstock is a non-ferromagnetic powder metalinjected into one or more discrete second regions in the mold, thediscrete second regions in alternating relation with the first discreteregions, whereby a composite powder metal component for a synchronousreluctance machine is formed having one or more magnetically conductingsegments alternating with one or more magnetically non-conductingsegments.
 43. The method of claim 18, wherein a first feedstock is asoft ferromagnetic powder metal injected into a first region in acylinder-shaped mold, the first region having a yoke and teethconfiguration, and a second feedstock is a non-ferromagnetic powdermetal injected into discrete second regions in the mold, the discretesecond regions positioned between the teeth of the first region, wherebya composite powder metal component for a switched reluctance machine isformed having a magnetically conducting segment and a plurality ofmagnetically non-conducting segments.
 44. A method of making a powdermetal rotor component for a surface permanent magnet machine, the methodcomprising: injecting a soft ferromagnetic powder metal from a firstinjection unit under heat and pressure into an inner annular region of acylinder-shaped mold; injecting a non-ferromagnetic powder metal from asecond injection unit under heat and pressure into discrete regionswithin an outer annular region of the mold so as to leave spaces betweeneach discrete region; injecting a hard ferromagnetic powder metal from athird injection unit under heat and pressure into the spaces between thediscrete regions of the outer annular region of the mold to provide anarrangement of alternating polarity permanent magnets; and allowing thepowder metals to solidify to thereby form a composite powder metalcomponent having an inner annular magnetically conducting segment and anouter annular segment of a plurality of alternating polarity permanentmagnets separated by magnetically non-conducting segments.
 45. Themethod of claim 44, wherein the soft ferromagnetic powder metal is Ni,Fe, Co or an alloy thereof.
 46. The method of claim 44, wherein the softferromagnetic powder metal is high purity iron powder with a minoraddition of phosphorus.
 47. The method of claim 44, wherein thenon-ferromagnetic powder metal is an austenitic stainless steel.
 48. Themethod of claim 44, wherein the non-ferromagnetic powder metal is anAISI 8000 series steel.
 49. The method of claim 44, further comprisingmounting the composite component on a shaft to form a powder metal rotorassembly.
 50. The method of claim 44, wherein the powder metals are eachcombined with a binder prior to injecting.
 51. The method of claim 50,further comprising the steps of: ejecting the composite component fromthe mold; subjecting the composite component to debinding to provide acomposite part which is essentially free of binder; and sintering thecomposite part.
 52. A method of making a powder metal rotor componentfor a circumferential type interior permanent magnet machine, the methodcomprising: injecting a soft ferromagnetic powder metal from a firstinjection unit under heat and pressure into an inner annular region of acylinder-shaped mold; injecting a non-ferromagnetic powder metal from asecond injection unit under heat and pressure into discrete firstregions within an outer annular region of the mold so as to leave spacesbetween each discrete first region; injecting the soft ferromagneticpowder metal from the first injection unit under heat and pressure intodiscrete second regions between the first regions so as to leave aradially inner circumferentially extending space and optionally leavinga radially extending space through each discrete second region;optionally injecting the non-ferromagnetic powder metal from the secondinjection unit under heat and pressure into the radially extendingspaces; injecting a hard ferromagnetic powder metal from a thirdinjection unit under heat and pressure into the radially innercircumferentially extending spaces between the discrete first regions ofthe outer annular region of the mold to provide an arrangement ofalternating polarity permanent magnets; and allowing the powder metalsto solidify to thereby form a composite powder metal component having aninner magnetically conducting segment and an outer permanent magnetsegment of a plurality of alternating polarity permanent magnetsseparated by magnetically non-conducting barrier segments and radiallyembedded by magnetically conducting segments with optional intermediatemagnetically non-conducting bridge segments.
 53. The method of claim 52,wherein the soft ferromagnetic powder metal is Ni, Fe, Co or an alloythereof.
 54. The method of claim 52, wherein the soft ferromagneticpowder metal is high purity iron powder with a minor addition ofphosphorus.
 55. The method of claim 52, wherein the non-ferromagneticpowder metal is an austenitic stainless steel.
 56. The method of claim52, wherein the non-ferromagnetic powder metal is an AISI 8000 seriessteel.
 57. The method of claim 52, further comprising mounting thecomposite component on a shaft to form a powder metal rotor assembly.58. The method of claim 52, wherein the powder metals are each combinedwith a binder prior to injecting.
 59. The method of claim 58, furthercomprising the steps of: ejecting the composite component from the mold;subjecting the composite component to debinding to provide a compositepart which is essentially free of binder; and sintering the compositepart.
 60. A method of making a powder metal rotor component for a spoketype interior permanent magnet machine, the method comprising: injectinga non-ferromagnetic powder metal from a first injection unit under heatand pressure into an inner annular region of a cylinder-shaped mold;injecting a soft ferromagnetic powder metal from a second injection unitunder heat and pressure into discrete first regions within an outerannular region of the mold so as to leave spaces between each discretefirst region; injecting the non-ferromagnetic powder metal from thefirst injection unit under heat and pressure into discrete radiallyouter second regions between the first regions so as to leave a radiallyinner radially extending space between each of the adjacent firstregions; injecting a hard ferromagnetic powder metal from a thirdinjection unit under heat and pressure into the radially extendingspaces between the discrete first regions of the outer annular region ofthe mold to provide an arrangement of alternating polarity permanentmagnets; and allowing the powder metals to solidify to thereby form acomposite powder metal component having an inner annular magneticallynon-conducting segment and an outer annular segment of a plurality ofalternating polarity permanent magnets separated by magneticallyconducting segments and embedded by magnetically non-conductingsegments.
 61. The method of claim 60, wherein the soft ferromagneticpowder metal is Ni, Fe, Co or an alloy thereof.
 62. The method of claim60, wherein the soft ferromagnetic powder metal is high purity ironpowder with a minor addition of phosphorus.
 63. The method of claim 60,wherein the non-ferromagnetic powder metal is an austenitic stainlesssteel.
 64. The method of claim 60, wherein the non-ferromagnetic powdermetal is an AMSI 8000 series steel.
 65. The method of claim 60, furthercomprising mounting the composite component on a shaft to form a powdermetal rotor assembly.
 66. The method of claim 60, wherein the powdermetals are each combined with a binder prior to injecting.
 67. Themethod of claim 66, further comprising the steps of: ejecting thecomposite component from the mold; subjecting the composite component todebinding to provide a composite part which is essentially free ofbinder; and sintering the composite part.
 68. A method of making apowder metal rotor component for an induction machine, the methodcomprising: injecting a soft ferromagnetic powder metal from a firstinjection unit under heat and pressure into a first region of acylinder-shaped mold to form a pattern of a plurality of equally spacedaxially extending slots adjacent an exterior circumferential surface ofthe cylinder-shaped mold; injecting a non-ferromagnetic powder metalfrom a second injection unit under heat and pressure into a plurality ofdiscrete second regions of the mold in a radially outer portion of eachslot adjacent the exterior circumferential surface, thereby formingclosed slot openings; and allowing the powder metals to solidify tothereby form a composite powder metal component having a magneticallyconducting segment and a plurality of magnetically non-conductingsegments enclosing slot openings.
 69. The method of claim 68, whereinthe soft ferromagnetic powder metal is Ni, Fe, Co or an alloy thereof.70. The method of claim 68, wherein the soft ferromagnetic powder metalis high purity iron powder with a minor addition of phosphorus.
 71. Themethod of claim 68, wherein the non-ferromagnetic powder metal is anaustenitic stainless steel.
 72. The method of claim 68, wherein thenon-ferromagnetic powder metal is an MISI 8000 series steel.
 73. Themethod of claim 68, further comprising mounting the composite componenton a shaft to form a powder metal rotor assembly.
 74. The method ofclaim 68, wherein the powder metals are each combined with a binderprior to injecting.
 75. The method of claim 74, further comprising thesteps of: ejecting the composite component from the mold; subjecting thecomposite component to debinding to provide a composite part which isessentially free of binder; and sintering the composite part.
 76. Amethod of making a powder metal rotor component for a synchronousreluctance machine, the method comprising: injecting a softferromagnetic powder metal from a first injection unit under heat andpressure into one or more discrete first regions in a cylinder-shapedmold; injecting a non-ferromagnetic powder metal from a second injectionunit under heat and pressure into one or more discrete second regions inthe mold, the discrete second regions in alternating relation with thediscrete first regions; and allowing the powder metals to solidify tothereby form a composite powder metal component having one or moremagnetically conducting segments and one or more magneticallynon-conducting segments.
 77. The method of claim 76, wherein the softferromagnetic powder metal is Ni, Fe, Co or an alloy thereof.
 78. Themethod of claim 76, wherein the soft ferromagnetic powder metal is highpurity iron powder with a minor addition of phosphorus.
 79. The methodof claim 76, wherein the non-ferromagnetic powder metal is an austeniticstainless steel.
 80. The method of claim 76, wherein thenon-ferromagnetic powder metal is an AISI 8000 series steel.
 81. Themethod of claim 76, further comprising mounting the composite componenton a shaft to form a powder metal rotor assembly.
 82. The method ofclaim 76, wherein the powder metals are each combined with a binderprior to injecting.
 83. The method of claim 82, further comprising thesteps of: ejecting the composite component from the mold; subjecting thecomposite component to debinding to provide a composite part which isessentially free of binder; and sintering the composite part.
 84. Amethod of making a powder metal rotor component for a switchedreluctance machine, the method comprising: injecting a softferromagnetic powder metal from a first injection unit under heat andpressure into a first region in a cylinder-shaped mold, the first regionhaving a yoke and teeth configuration; injecting a non-ferromagneticpowder metal from a second injection unit under heat and pressure intodiscrete second regions in the mold, the discrete second regionspositioned between the teeth of the first region; and allowing thepowder metals to solidify to thereby form a composite powder metalcomponent having a magnetically conducting segment and a plurality ofmagnetically non-conducting segments.
 85. The method of claim 84,wherein the soft ferromagnetic powder metal is Ni, Fe, Co or an alloythereof.
 86. The method of claim 84, wherein the soft ferromagneticpowder metal is high purity iron powder with a minor addition ofphosphorus.
 87. The method of claim 84, wherein the non-ferromagneticpowder metal is an austenitic stainless steel.
 88. The method of claim84, wherein the non-ferromagnetic powder metal is an AISI 8000 seriessteel.
 89. The method of claim 84, further comprising mounting thecomposite component on a shaft to form a powder metal rotor assembly.90. The method of claim 84, wherein the powder metals are each combinedwith a binder prior to injecting.
 91. The method of claim 90, furthercomprising the steps of: ejecting the composite component from the mold;subjecting the composite component to debinding to provide a compositepart which is essentially free of binder; and sintering the compositepart.
 92. A method of making a powder metal rotor sense ring, the methodcomprising: injecting a powder filler material from a first injectionunit under heat and pressure into an inner annular region of acylinder-shaped mold; injecting a non-ferromagnetic powder metal from asecond injection unit under heat and pressure into discrete regionswithin an outer annular region of the mold so as to leave spaces betweeneach discrete region; injecting a hard ferromagnetic powder metal from athird injection unit under heat and pressure into the spaces between thediscrete regions of the outer annular region of the mold to provide anarrangement of alternating polarity permanent magnets; and allowing thepowders to solidify to thereby form a composite powder metal componenthaving an inner annular filler segment and an outer annular segment of aplurality of alternating polarity permanent magnets separated bymagnetically non-conducting segments.
 93. The method of claim 92,wherein the non-ferromagnetic powder metal is an austenitic stainlesssteel.
 94. The method of claim 92, wherein the non-ferromagnetic powdermetal is an AISI 8000 series steel.
 95. The method of claim 92, furthercomprising mounting the composite component on a shaft to form a powdermetal rotor assembly.
 96. The method of claim 92, wherein the powdermetals are each combined with a binder prior to injecting.
 97. Themethod of claim 96, further comprising the steps of: ejecting thecomposite component from the mold; subjecting the composite component todebinding to provide a composite part which is essentially free ofbinder; and sintering the composite part.
 98. A composite injectionmolded rotor component for a rotor assembly comprising a first region ofan injection molded soft ferromagnetic powder metal, a second region ofan injection molded non-ferromagnetic powder metal, and optionally athird region of an injection molded hard ferromagnetic powder metal.